How Does UUCP Work?

UUCP also supports Usenet, a bulletin−board network that uses the public domain Netnews software to exchange news about a wide variety of topics. 24.4.1 How Does UUCP Work? Using UUCP basically means dealing with three main programs: uucp, for a file transfer to or from a remote machine similar to the cp program; however, with extended addressing capabilities 1. uux, for a command execution on a remote machine usually restricted in some way because of security reasons 2. mail, a version of a mail program that is compatible with UUCP this is binmail; it should not be confused with usrucbmail that is an e−mail user agent that was discussed in the Chapter 20 3. The listed programs are user related, i.e., they are primarily used from the command line. However, it happens much more in the background; two running UUCP daemons, uucico and uuxqt, invisible to users actually do most of the work. uucico is involved in transferring files and remote execution requests between UNIX systems, and uuxqt in their processing on a remote UNIX system. UUCP is a store−and−forward subsystem: requests for transfer and remote processing are not executed immediately; instead they are spooled for later execution. UUCP daemons take care of spooled requests and process them once the connection between remote UNIX systems has been established. A more detailed description of what happens is: When uucp or uux programs are invoked, a work file containing information about the source and destination files, the program options, and the type of requests is created in the directory usrspooluucp. If a file transfer was required, a file to be transferred is also copied. • The uucico daemon is involved to make the transfer; it scans the spool directory for work files and attempts to contact specified remote UNIX systems and execute the instructions in the work files. In the BNU UUCP version, an intermediate process called uusched does the scan and calls uucico when the needed conditions are met. • The work files contain only a part of the information uucico needs to know: what to do, but not when or how to do it. This information is contained in a set of the UUCP configuration files in the directory usrlibuucp, and this is a duty of the system administrator to set up in advance. •

24.4.2 UUCP Versions